Load-handling apparatus

ABSTRACT

An improved stacker crane includes a shuttle assembly for depositing loads in storage racks or bins and for retrieving the loads from the bins. The shuttle assembly is extendible from a retracted condition to either one of two opposite extended conditions. When the shuttle assembly is operated between the extended and retracted conditions, an intermediate section of the shuttle assembly is moved through a first distance at a first speed relative to a base section of the shuttle assembly. Simultaneously therewith, a load-supporting section of the shuttle assembly is moved relative to the intermediate section through a second distance which is greater than the first distance at a second speed which is greater than the first speed. A shock absorber assembly is provided for retarding movement of the shuttle assembly when it approaches the retracted condition or either one of the extended conditions.

United States Patent [72] Inventors Stephen F. Aaronson 2,788,905 4/ I957 Grove 214/1 6.42 UX Philadelphia; 3,232,455 2/1966 Fountain et al..... 2l4/l6.4 (2) Alvin B. Garnish, Wrlghtstown; Erriclt G. 3,240,364 3/l966 Kapnek et al 2l4/730 X Primary Examiner-Robert o. Sheridan 2133 Attorney-Yount, Flynn &. Tarolli Patented Aug. 3, I971 g E8")! lllc- ABSTRACT: An improved stacker crane includes a shuttle assembly for depositing loads in storage racks or bins and for retrieving the loads from the bins. The shuttle assembly is extendible from a retracted condition to either one of two op- [54] LOADJIANDUNG APPARATUS posite extended conditions. When the shuttle assembly is m Chm l5 Dn'in' F V operated between the extended and retracted conditions, an intermediate section of the shuttle assembly is moved through 214/730, a first distance at a first speed relative to a base section of the 214/16-4 shuttle assembly. Simultaneously therewith, a load-supporting I 8 65/2 section of the shuttle assembly is moved relative to the intermediate section through a econd distance is greater 16.42, 730; 104/25 than the first distance at a second speed which is greater than the first speed. A shock absorber assembly is provided for re- [56] Ream cm tarding movement of the shuttle assembly when it approaches UNITED STATES PATENTS the retracted condition or either one of the extended condi- 638,2l3 12/1899 Clark 104/256 tions.

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sum 6 OF 8 FIGS INVENTOR3 STEVE/V AAROMSOA/ Al. WA! 5 GA/PN/CH zEAW/CK G. MOAIP/S ATTORNEYS LOAD-HANDLING APPARATUS This invention relates generally to a stacker crane having an improved shuttle assembly for moving loads.

A known stacker crane includes a shuttle assembly which is operable between a retracted condition and either one of two opposite extended conditions to deposit loads in and to retrieve loads from opposing rows of storage racks or bins. The shuttle assembly is driven between the extended and retracted conditions by a plurality of pinions, one set of pinions being utilized when the shuttle assembly is extended in one direction and another set of pinions being utilized to extend the shuttle assembly in the opposite direction. While shuttle assemblies having this known pinion drive have proven to be generally satisfactory, the pinion drive arrangement has caused design and fabrication difl'rculties. In addition, this known pinion drive arrangement has proven to be rather inflexible as to the distance to which a load platform of the shuttle assembly can be extended and the speed at which the load platform is moved between the retracted and extended conditions.

Accordingly, it is an object of this invention to provide a stacker crane having a new and improved shuttle assembly which is compact, reliable in operation, easily designed and fabricated, and flexible as to future applications.

Another object of this invention is to provide a stacker crane having a new and improved shuttle assembly wherein a load platform is moved outwardly for a comparatively large distance relative to an inter-mediate section on which it is mounted upon operation of the shuttle assembly to an extended condition.

Another object of this invention is to provide a stacker crane having a new and improved'shuttle assembly with a load platfonn which is moved outwardly at a relatively high speed upon operation of the shuttle assembly to an extended condition.

Another object of this invention is to provide a stacker crane having a new and improved shuttle assembly with a single shock absorber assembly for retarding movement of the shuttle assembly when it approaches a retraeed condition or either one of two extended conditions.

Another object of this invention is to provide a stacker crane having a shuttle assembly with a new and improved drive mechanism for moving a load platfonn of the shuttle assembly between retracted and extended conditions.

Another object of this invention is to provide a stacker crane having a shuttle assembly with a new and improved drive mechanism in accordance with the preceding paragraph wherein the shuttle drive mechanism includes a first pinion which is driven in response to movement of an intermediate section of the shuttle assembly relative to a base section of the shuttle assembly and a second pinion which is driven in response to rotation of the first pinion to move the load platform of the shuttle assembly between extended and retracted conditions, the second pinion having a larger diameter than the first pinion to thereby effect movement of the load platform through a relatively large distance at a high speed upon movement of the intermediate section through a smaller distance at a lower speed.

These and other objects and features of the invention will become more apparent upon a consideration of the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a schematic elevational view of a stacker crane constructed in accordance with the present invention;

FIG. 2 is a schematic view, taken along the line 2-2 of FIG. 1, illustrating the relationship of the stacker crane to a plurality of rows of bins or storage racks;

FIG. 3 is an enlarged sectional view of a shuttle assembly of the stacker crane of FIG. I;

FIG. 4 is a greatly enlarged sectional view, generally similar to FIG. 3, further illustrating the structure of the shuttle assembly;

FIG. 5 is a schematic illustration of the shuttle assembly in an extended condition;

FIG. 6 is a schematic illustration of the shuttle assembly in a retracted condition;

FIG. 7 is a schematic illustration showing the drive arrangement for moving the shuttle assembly between the retracted and extended conditions;

FIG'. 8 is an enlarged schematic illustration of the shuttle assembly drive of FIG. 7;

FIG. 9 is an enlarged, fragmentary illustration of a portion of the shuttle assembly drive of FIG. 8;

FIG. 10 is an enlarged schematic view of a shock absorber assembly for retarding movement of a load platform of the shuttle assembly when the shuttle assembly approaches either the retracted or extended conditions, the shock absorber assembly being depicted in FIG. 10 with the shuttle assembly in the retracted condition;

FIG. 11 is a schematic view, similar to FIG. 10, illustrating the shock absorber assembly when the shuttle assembly is in an extended condition;

FIG. 12 is a schematic view illustrating the shock absorber assembly in its neutral or unoperated condition;

FIG. 13 is a schematic illustration depicting the positions of a plurality of control or sensor switches when the shuttle assembly is in the retracted condition;

FIG. 14 is a schematic illustration depicting the positions of the sensor switches whenthe shuttle assembly is in an extended condition; and

FIG. 15 is a schematic illustration of a shuttle assembly control circuit which includes the sensor switches of FIGS. 13 and A stacker crane embodying the present invention includes a shuttle assembly which is operable between a retractedcondition and either one of two extended conditions to deposit loads in and retrieve loads from opposing rows of bins or storage racks. This shuttle assembly includes a drive mechanism for moving a load platform or supporting section relative to an intermediate section while the intermediate section is being moved relative to a base section. In accordance with a feature of the present invention, the drive mechanism is operable to move the load platform through a greater distance relative to the intermediate section than the distance which the intermediate section is moved relative to the base section while the shuttle assembly is being operated between the retracted and extended conditions. To accomplish this, the drive mechanism moves the load platform relative to the intermediate section at a greater speed than the speed at which the intermediate section is moved relative to the base section. The shuttle assembly'advantageously includes a shock absorber assembly for retarding movement of the load platform when the shuttle assembly approaches the retracted or either one of the extended conditions to thereby minimize shock forces applied to parts of the shuttle assembly and to loads supported on the load platform. I

A stacker crane 20 (FIGS. 1 and 2 is operable to deposit loads 22 in and to remove loads from storage bins or racks 24. The storage bins 24 are arranged in a plurality of opposing rows 28 and 30 which face toward each other to define an aisle 32 (FIG. 2) along which the stacker crane 20 can be moved. To provide for this movement, the stacker crane is mounted on a pair of wheels 34 (only one of which is shown in the drawings) which engage a floor or lower rail 36 located between the rows 28 and 30 of bins. A suitable drive motor 40 (FIG. 1) is mounted on a base 42 of the stacker crane and is selectively operable to drive one of the wheels 34 to move the stacker crane in either of two opposite directions along the aisle 32.

After the stacker crane 20 has been moved to a position adjacent to a selected column of bins 24 by operation of the drive motor 40, a load 22 must be raised to position it venically relative to a selected one of the bins. To this end, a carriage assembly 44 is moved upwardly along a mast or frame assembly 46 having a pair of opposite side sections 48 by operation of a carriage drive or lift motor 50. When the carriage assembly 44.is directly adjacent to the selected one of the bins 24, a shuttle assembly 54 is operated'from a retracted condition (shown in FIGS. 2 and 6) to an extended condition (see FIGS. and 7) to enable the load 22 to be deposited in the selected bin. It should be noted that the shuttle assembly 54 can be operated from the retracted condition to either of two opposite'extendcd conditions, that is to an extended condition in which the shuttle assembly projects outwardly to either the left or the right as viewed in FIG. 2. "This enables the shuttle assembly 54 to be used to deposit a load- 22 in and retrieve a load from either of facing rows 28 and 30 of bins or storage racks 24.

To deposit a load 22 in a selected one of the bins 24, the shuttle assembly 54 is extended with the load'slightly above horizontal suppon angles or members 58 which are connected to vertically extending side members 60. The carriage 44 is then lowered to rest the load 22 on the support members or angles 58 while the relatively narrow shuttle assembly 54 moves downwardly through the space between the angles which cooperate to engage the support the load 22 (FIG. 1). The shuttle amembly 54 is then operated to the retracted condition to enable the stacker crane to be moved along the aisle 32. i

When a load 22 is to be retrieved from a selected one of the bins 24, the stacker crane 20 is moved along the aisle 32 to a position adjacent to a vertical column of bins in which the selected bin is located. The carriage 44 is then raised to position the shuttle assembly 54 in a location immediately below the selected bin. Thereupon the shuttle assembly 54 is operated to the extended condition. The lift motor 50 is then operated to raise the carriage alembly 44 so that the selected load 22 is engaged by the shuttle assembly 54 and lifted upwardly of! the support brackets 58. The shuttle assembly. 54 is then operated to the retracted condition to enable the stacker crane 20 and the selected load to be moved along the aisle 32 by operation of the crane drive motor 40. Of course, the shuttle assembly 54 can be extended to either the right or the left as viewed in FIG. 2 to retrieve a load from either of the rows 28 and 30 of bins 24.

The upper end of the mast 46 will an upper or ceiling support rail 64 to retain the stacker crane 20 against tilting when the shuttle assembly 54 is in an extended condition. A stabilizing assembly 68 maintains the mast 46 in an upright position while the stacker crane 20 is being moved along the rails 36 and 64 by operation of the crane drive motor 40. The stabilizing assembly 68 includes a pair of identical pinion gears 72 and 74 which engage elongated rack gears 76 and 78 respectively. The rack gears 76 and 78 extend parallel to each other and the rails 36 and 64. Upon movement of the stacker crane 20 along the support tracks or rails 36 and 64, the pinion gears 72 and 74 are rotated at the same speed through a shaft assembly 80 to maintain the stacker crane 20 in the upright position of FIG. 1 and prevent the upper end portion of the stacker crane from tilting relative to the base 42 as it is moved along the tracks 36 and 64.

Since the a'ale 32 should be relatively narrow to provide for efficient utilization of the available storage space, the shuttle assembly 54 telescopes from the extended condition to a relatively compact retracted condition. This telescoping characteristic is provided for by mounting a load platform or table 84 for movement relative to an intermediate section 86 which is in turn movable relative to the base section 88 (see FIGS. 3, 4 and 5). To enable the load platform 84 and intermediate section 86 to move freely relative to each other and the base section 88, rollers 92 are mounted on side members or rails 94 and 96 of the load platforrn84 (FIG. 3). The rollers 92 roll along a channel defined by the side rails 98 and 100 of the intermediate section 86. Similarly, rollers 104 and 106 are mounted on the side rails 98 and 100 of the intermediate section 86 and roll along channels formed by side rails or members 110 and 112 ofthe base section 88.

When the shuttle assembly 54 is in the retracted condition of FIG. 6, the load platform 84, intermediate section 86 and base section 88 are telescoped together to provide a compact assembly which can be readily moved along the relatively narrow aisle 32 (FIG. 2) When the shuttle assembly 54 is operated to the extended condition, the intermediate section 86 is moved outwardly relative to the base section 88 while the load platform 84 is moved outwardly relative to the inter mediate section 86 (FIG. 5). Although the shuttle assembly is depicted in FIG. 5 as being operated to an extended condition toward the right, it should be understood that the shuttle assembly 54 can also be operated to a similar extended condition toward the left.

In accordance with a feature of the present invention, the load platform 84 of the shuttle assembly 54 is moved through a larger distance relative to the intermediate section 86 than the distance which the intermediate section is moved relative to the base section 88 upon operation of the shuttle assembly between the retracted condition and either of the extended conditions. To provide for this movement of the load platform 84, a shuttle drive mechanism 116 (FIGS. 3, 4 and 7) is operable to move the load platform 84 at a greater speed relative to the intermediate section 86 than the speed of which the intermediate section-is moved relative to the base section. This relatively fast movement of the load platform 84 through a relatively large distance upon operation of the shuttle assembly 54 enables the shuttle assembly to be extended for relatively large distances toward the right or left from the compact retraoed condition of FIG. 6.

Upon operation of the shuttle assembly 54 between the retraced and extended conditions, a pair of pinion gears 120 and 122 (FIG. 3) are rotated by a shuttle drive assembly 124 having a reversible motor 125 to which the pinion gears are connected by a common drive shaft 126. Rack gears and 132 are mounted on the opposite side members or rails 98 and 100 of the intermediatev section 86 and mesh with the associated ones of the pinion gears 120 and 122. Therefore, upon rotation of the gears 120 and 122 by operation of the drive auembly 124, the intermediate section 86 is moved relative to the base section 88. If the pinion gears I20 and 122 are rotated in a clockwise direction as viewed in FIG. 7 when the shuttle assembly 54 is inthe retracted condition of FIG. 6, the intermediate section 86 is moved toward the rightward extended position shown in FIG. 7. Similarly, upon rotation of the pinion gears 120 and 122 in the counterclockwise direction (as viewed in FIG. 7) when'the shuttle assembly 54 is in the retracted condition of FIG. 6, the intermediate section 86 is moved toward a leftward extended position. Of course, the intermediate section 86 is moved toward the retracted position of FIG. 6 from either a rightward or leftward extended position by reversing the previous rotation of the pinion gears 120 and 122.

The shuttle drive mechanism 116 includes a load platform drive assembly 136 (see FIG. 4) which is operated in response to movement of the intermediate section 86 relative to the base section 88. Operation of the drive'assembly 136 moves the load platform 84 in the same direction and at a speed which is more than twice as great as the speed at which the intermediate section 86 is moved. To provide for this movement of the load platform 84, the drive assembly 136 includes two sets of pinions or sprockets 140 and 142 (FIGS. 7, 8 and 9) which are mounted at opposite ends of the intermediate section 86 on parallel axles 144 and 146.

The sprocket set 140 (FIG. 4) includes a pair of relatively small pinions or sprockets 148 and 150 which are secured to the axle 144. The axle 144 is in turn rotatably mounted on a pair of support sections 151 and 152 which are secured to the opposite support rails or members 98 and 100 of the intermediate section 86 (FIG. 3). The sprocket 150 engages a chain loop 154 having a portion 156 secured to the base section 88 by a suitable bracket 160 (see FIGS. 4, 7 and 8). Since the portion 156 of the chain loop 154 is secured to the base section 88, movement of the intennediate section 86 relative to the base section 88 causes the sprocket 150 to interact with the chain loop to rotate the axle 144.

A chain loop 166 (FIG. 4) is associated with the small sprocket 148 in much the same manner as in which the chain loop 154 is associated with the sprocket 150. The chain loop 166 has a portion 168 which is secured to the base section 88 by a suitable bracket 170. Therefore, upon movement of the intermediate section 86 relative to the base section 88, the sprocket 148 is rotated by the associated chain loop 166.

The sprocket set 140 also includes a pair of large pinions or sprockets 176 and 178 which are mounted on the shaft 144 and mesh with chain racks 182 and 184 which are connected to the load platform 84. Therefore upon rotation of the shaft 144 by the small sprockets 148 and 150, the large sprockets 176 and 178 are rotated to move the load platform 84 relative to the intermediate section 86 by meansof the chain racks 182 and 184. Since the sprockets 176 and 178 have a larger 'efi'ective diameter than the sprockets I48 and 150, the load platform 84 is moved relative to the intermediate section 86 by the larger sprockets 176 and 178 at a greater speed than the speed at which the intermediate section 86 is moved relative to the base section 88.

The sprocket set 142 (FIGS. 8 and 9) is substantially the same as the sprocket set 140 and includes a pair of small pinions or sprockets which cooperate with the chain loops 154 and 166 in much the same manner as do the small sprockets 148 and 150. Thus, the sprocket set 142 includes a small sprocket 185 having the same effective diameter as the small sprocket 150 of the sprocket set 140. The small sprocket 185 meshingly engages the chain loop 154 and is rotated by the chain loop when the intermediate section is moved relative to the base section 88 by rotation of the pinion gears 120 and 122.

Rotation of the small sprocket 185 rotates the shaft 146 on which a large sprocket 186 is mounted in meshing engagement with the chain rack 184. The large sprocket 186 has the'same effective diameter as the large sprocket 176. Therefore, upon movement of the intermediate section 86 relative to base section 88, the small sprocket 185 is driven by the chain loop 154 to rotate the large sprocketl86. Since the large sprocket 186 is mounted in meshing engagement with the chain rack 184 on the load platform 84, the load platform is moved by the large sprocket 186 relative to the intermediate section 86.

The sprocket set 142 also includes small and large sprockets (not shown) which are the same as the small and large sprockets 185 and 186. These sprockets are mounted on the shaft 146 in meshing engagement with the chain loop 166 and chain rack 182 in much the same manner as illustrated in FIG. 4 for the large and small sprockets 148 and 176. It should be noted that the large sprockets (only the sprocket 186 being shown) of the sprocket set 142 cooperate with the chain racks 182 and 184 when the shuttle assembly is operated to the rightward extended condition as viewed in FIGS. 7 and 8. Similarly, when the shuttle assembly 54 extended to the left (as viewed in FIGS. 7 and 8), the larger sprockets 176 and 178 of the sprocket set 140 cooperate with the chain racks 182 and 184 to move the load platform 84 relative to the intermediate section 86.

The shuttle assembly 54 includes a single shock absorber assembly 190 (FIGS. l0, l1 and 12) for minimizing the shock load on components of the shuttle assembly and on a load supported by the platform-section 84 when the shuttle assembly is operated from the retracted condition to either of the extended conditions. The shock absorber assembly 190 includes a pair of single action shock absorbers 192 and 194 which are pivotally connected at 196 and 198 to the base section 88. Connecting rods 202 and 204 of the shock absorbers 192 and 194 are pivotally connected to arms 206 and 208 (see FIGS. 4 and 10) of a stop lever assembly 210. The stop lever assembly 210 includes a cylindrical body section2l4 which is rotatably mounted on a sleeve 216 around the drive shah 126.

When the shuttle assembly 54 approaches the retracted FIG. 7, the shock absorber assembly 190 is operated to retard movement of the load platform 84. Accordingly, as the shuttle assembly 54 approaches -the retracted condition, the stop lever assembly 210 is pivoted from an upright or neutral condition (FIG. 12) to an operated condition (FIG. 10) against the influence of the shock absorber 194. This pivoting of the stop lever assembly 210 results from engagement of a stop surface 222 on a central stop member 224 with a stop roller 228 mounted between the stop arms 206-and 208 (see FIG. 10 taken in conjunction with FIG. 4). Operation of the shock absorber 194 at least partially absorbs the kinetic energy of the shuttle assembly 54 to thereby minimize shock loading on the parts of the shuttle assembly and any load which may be on the load platform 84.

Upon subsequent initiation of. operation of the shuttle assembly to a leftward extended condition (as viewed in FIG. 10), the shuttle drive assembly 1 16 is operated to move the intermediate section 86 toward the left. This movement causes the stop member 224 to override the shock absorber assembly 190 and press the stop lever assembly 210 downwardly to the position indicated in dashed lines in FIG. 10. After the stop member 224 has been moved toward the left past the stop condition of FIG. 6 from the rightward extended condition of lever assembly 210, the stop lever assembly is pivoted to the upright or neutral condition of FIG. 12 by the shock absorber 194. As the shuttle assembly 54 approaches the leftward extended condition, as viewed in FIG. 10, stop surface 236 on a stop member 238 engages the upright stop lever assembly 210 and pivots it to the position shown in solid lines in FIG. 10 against the influence of the shock absorber 194. Of course, this retards the movement of the shuttle assembly 54 toward the leftward extended condition to thereby minimize shock loading on the shuttle assembly when it reaches the extended condition.

When operation of the shuttle assembly 54 from the leftward extended condition is initiated, the stop member 238 moves away from the stop lever assembly 210. Thereupon the stop lever assembly 210 is pivoted to the upright condition of FIG. 12 by the shock absorber 194. Continued movement of the shuttle assembly toward the retracted condition brings a second stop surface 240 on the stop member 224 into engagement with the stop lever assembly 210. This pivots the stop lever assembly 210 to an operated condition (similar to that shown in FIG. 11) against the influence of the shock absorber 192.

Subsequent operation of the shuttle assembly 54 to a rightward extended condition causes the stop member 224 to override the shock absorber assembly l'by pivoting stop lever assembly 210 clockwise from the position shown in FIG. 11. After the stop member 224 has moved past the stop lever assembly 210, it pivots to the upright condition of FIG. 12. Continued movement of the shuttle assembly 54 toward the rightward extended condition brings a stop surface 242 on a stop member 244 into engagement with the stop lever assembly 210 to pivot the assembly from the upright condition of FIG. 12 to the operated condition of FIG. 1 1 against the influence of the shock absorber 192. Of course, this decelerates the shuttle assembly 54 to minimize shock loads on the shuttle assembly when it reaches the rightward extended condition.

The stop members 224, 238 and 244 are fixedly secured to a support plate or section 250 which extends between the side members 98 and 100 (see FIG. 3) of the intermediate section 86. Since the support plate 250 is located between the axles 144 and 146 (FIG. 10) it does not interfere with movement of the intermediate section 86 relative to the base section 88. The stop members 224, 238 and 244 are aligned with each other and the stop lever assembly 210 to enable the single shock absorber assembly 190 to be operated upon operation of the shuttle assembly 54 between the retracted and extended conditions.

A plurality of sensor switches 260, 262, 264, 266 and 268 (see'FIGS. 13, I4 and 15) are provided for interrupting the operation of the shuttle drive motor when the shuttle assembly approaches the retracted condition or either one of the extended conditions. When the shuttle ssembly 54 approaches the retracted condition (FIG. 13), the normally closed sensor switch 264 is actuated to the open condition by an actuator member or arm 272 (see FIG. 3). Actuation of the sensor switch 264 interrupts the operation of the shuttle drive motor 125'. This enables the shock absorber assembly 190 to efiectively stop the shuttle assembly 54 in the retracted condition of FIG. 13. The actuator member 272 then holds the sensor switch 264 on the open condition.

Operation of the shuttle assembly 54 toward one of the extended conditions is initiated by actuating a normally open right start switch 276 or a nonnally open left start switch 278 (see FIG. to energize the reversible shuttle drive motor 125. Upon operation of the right start switch 276, a right relay 282 is energized to actuate control circuitry and energize the motor 125. This initiates operation of the shuttle assembly 54 from the retracted condition of FIG. 13 toward the rightward extended condition of FIG. 14. In addition, energization of the right control relay 282 closes relay contacts 284 (FIG. 15).

The initial movement of the intermediate section 86 toward a rightward extended condition moves the actuator arm 272 away from the sensor switch 264 so that it returns to its normal or closed condition. This completes a holding circuit for the control relay 282 through the normally closed sensor switches 266 and 268, the sensor switch 264, and the now closed contacts 284 of the control relay 282. After movement of the shuttle assembly 54 toward the extended condition has been initiated and the holding circuit completed, the right start switch 276 is released. As the shuttle assembly 54 approaches the rightward extended condition of FIG. 14, the shock absorber assembly 190 is operated and the actuator arm 272 operates the sensor switch 266. Operation of the sensor switch 266 interrupts the holding circuit for the control relay 282 and stops the operation of the motor assembly 124. At the same time, the sensor switch 268 is operated to the open condition by an actuator member 288 (FIGS. 4 and 14). The sensor switch 268 insures that the load platform 84 is not moved past its normal rightward extended condition due to some unforeseen circumstance.

To return the shuttle assembly 54 to the retracted condition, the left start switch 278 (FIG. 15) is operated to the closed condition to complete a circuit through the normally closed sensor switches 262 and energize a left control relay 292. Energization of the left control relay 292 results in the shuttle drive motor 125 being operated in the reverse direction to thereby initiate movement of the shuttle assembly 54 toward the retracted condition of FIG. 13. In addition to energizing the shuttle drive motor 125, operation of the relay 292 to provide a holding circuit through the now closed sensor switch 264 and the sensor switches 260 and 262. The left start switch 278 can then be released by the operator. When the shuttle assembly 54 reaches the retracted condition of FIG. 13, the sensor switch 264 is operated to the open condition by the actuator member 272 to interrupt the holding circuit for the left control relay 292. Interruption of this holding circuit results in the relay 292 and motor assembly 124 being deenergized.

If the shuttle assembly 54 is to be operated to the leftward extended condition from the retracted condition of FIG. 13 the left start switch 278 is operated to energize the left control relay 292 and close the relay contacts 296. This results in the shuttle drive motor 125 being energized for rotation in a direction to effect movement of the shuttle assembly 54 toward the leftward extended condition. Initial movement of the shuttle assembly 54 toward the leftward extended condition moves the actuator arm 272 away from the sensor switch 264 to complete the holding circuit for the relay 292.

When the shuttle assembly 54 reaches the leftward extended condition, the actuator arm 272 operates the sensor switch 260 to interrupt the holding circuit for the relay 292. In

addition, the sensor switch 262 is operated by an actuator member 300 (see FIGS. 4 and 14) to insure that the load platform 84 is not moved past its normal leftward extended condition due to some unforeseen circumstance. Of course. the deenergization of the lefl control relay 292 stops the operation of the shuttle drive motor and enables the shock absorber assembly 190 to stop the shuttle assembly 54 in its leftward extended condition.

The shuttle assembly 54 is subsequently returned to the retracted condition of FIG. 13 from the leftward extended condition by actuating the right start switch 276 (FIG. 15). Actuation of the right start switch 276 energizes the right control relay 282 to close the holding contacts 284 and initiate reverse operation of the shuttle drive motor 124. When the shuttle assembly 54 approaches the retracted condition, the actuator arm 272 again operates the sensor switch 264 to the open condition to interrupt the holding circuit for the relay 282. The shock absorber assembly 190 then stops the shuttle assembly 54 in its retracted condition.

In view of the foregoing remarks, it can be seen that the stacker crane 20 has a shuttle assembly 54 which is operable between a retracted condition and either one of two extended conditions. This enables the shuttle assembly 54 to be used to deposit loads in and remove loads from bins 24 on either side vof the aisle 32. The shuttle assembly 54 is operated between the extended and retracted conditions by a shuttle drive mechanism 116 which moves the load platform 84 relative to the intermediate section 86 at a higher speed than the speed at which the intermediate section is moved relativeto the base section 88. Since the load platform 84 is moved at a relatively high speed relative to the intermediate section 86, the load platform is moved through a greater distance relative to the intermediate section 86 than the distance which the intermediate section is moved relative to the base section 88 upon operation of the shuttle assembly 54 between the retracted and extended conditions. 7

To provide for the high-speed movement of the load platform through a large distance relative to the intermediate section 86, the shuttle drive mechanism 116 includes a pair of sprocket sets I40 and 142 including small pinions or sprockets I48 and which are driven in response to movement of the intermediate section 86 relative to the base section 88. A pair of large pinions or sprockets 176 and 178 are rotated by the rotation of the small sprockets 148 and 150 to move the load platform 84 relative to the intermediate section 86. Due to the relatively large effective diameter of the sprockets 176 and 178, the load platform 84 is moved relative to the intermediate section at a greater speed than the speed at which the intermediate section is moved relative to the base section 88.

A single shock absorber assembly is provided for retarding movement of the shuttle assembly 54 when it approaches the retracted condition or either of the extended conditions to thereby minimize shock loads on the parts of the shuttle assembly and a load carried by the shuttle assembly. As the shuttle assembly approaches the retracted condition or either of the extended conditions, the operation of the shuttle drive mechanism 116 is interrupted by actuation of certain of the sensor switches 260 and 268. It should be noted that the drive mechanism 116, the shock absorber assembly 190 and the sections 84, 86 and 88 of the shuttle assembly are interrelated in such a manner as to provide a relatively compact shuttle assembly 54 which can be easily fabricated.

Although the shuttle assembly 54 has been illustrated herein and in association with the stacker crane 20, it is contemplated that theshuttle assembly 54 will be used in many different environments. To the end of enabling the shuttle assembly 54 to be used in different environments, the distance through which the load platform 84 is moved upon operation of the shuttle assembly 54 and the speed of this movement can be varied. The distance and speed at which the load platform 84 is moved relative to the base section 88 are varied by merely varying the difference in the effective diameters between the small sprockets or pinions 148 and 150 and the larger sprockets or pinions 176 and 178. Varying the difference in the effective diameters between these sprockets varies the drive ratio between the intermediate section 86 and the load platform 84 to thereby vary both the distance through which the load platform 84 is moved relative to the intennediate section and the speed of this movement. In addition, the adapt ability of the shuttle assembly 54 for use in different environments is further enhanced by the compactness of the shuttle assembly when it is in the retracted condition.

Having described our invention, we claim:

1. A shuttle assembly operable between a retracted condition and an extended condition to move a load, said shuttle assembly comprising a base section, an intermediate section operatively connected with the mounted for movement relative to said base section, a load supporting section operatively connected with and mounted for movement relative to said intermediate section, and drive means for moving said intermediate section through a first distance relative to said base section upon operation of said shuttle assembly between the retracted and extended conditions and for moving said load supporting section through a second distance relative to said intermediate section upon operation of such shuttle assembly between the retracted and extended conditions, said second distance being larger than said first distance so that said load supporting section projects further from said intermediate section than said intermediate section projects from said base section when said shuttle assembly is in the extended condition; the improvement comprising drive means including a first drive chain having a portion fixedly secured to said base section, first sprocket means which is operatively connected to said intermediate section and cooperates with said first drive chain, a second drive chain having a portion fixedly secured to said load supporting section, and second sprocket means which cooperates with said second drive chain and is rotated in response to rotation of said first sprocket means to thereby effect the aforesaid movement of said load supporting section, said first sprocket means being rotated in response to the aforesaid movement of said intermediate section relative to said base section.

2. A shuttle assembly as set forth in claim 1 wherein said second sprocket means has a larger effective diameter than said first sprocket means to enable said drive means to move said load supporting section relative to said intermediate section at greater speed than the speed at which said intermediate section is moved relative to said base section upon operation of said shuttle assembly between the retracted and extended conditions. I

3. A shuttle assembly as set forth in claim 1 further including shock absorber means for retarding movement of said load supporting and intermediate sections whensaid shuttle assembly approaches either one of said extended and retracted conditions.

4. A shuttle assembly as set forth in claim 1 wherein said drive means is operable to extend and shuttle assembly in either of two opposite direction from said retracted condition to either of two extended conditions, said shuttle assembly further including a shock absorber assembly operatively connected with said base and load-supporting sections, first stop means for operating said shock absorber assembly when said shuttle assembly approaches one of said extended conditions, second stop means for operating said shock absorber assembly when said shuttle assembly approaches the other extended condition, and third means for operating said shock absorber assembly when said shuttle assembly approaches said retracted condition from either of said operated conditions.

5. A shuttle assembly as set forth in claim 4 wherein said first, second and third means are all mounted for movement with said intermediate section and are all aligned along a plane extending parallel to the path of movement of said shuttle assembly between said retracted and extended conditions.

6. A shuttle assembly operable between a retracted condition and either of two extended conditions to move a load, said shuttle assembly comprising a base section, a load supporting section movable relative to said base section, drive means for moving said load-supporting section in one tended condition, operatively connected with said base sec- I tion, first stop means operatively connected with said load supporting section for operating said shock absorber assembly when said shuttle assembly is approaching the one extended condition, second stop means spaced from said first stop means and operatively connected with said load supporting section for operating said shock absorber assembly when said shuttle assembly is approaching the other extended condition, and third means located between said first and second stop means and operatively connected with said load-supporting section for operating said shock absorber assembly when said shuttle assembly is approaching the retracted condition from either of the extended conditions.

7. A shuttle assembly as set forth in claim 6 wherein said third means includes a first surface for effecting operation of said shock absorber assembly when said shuttle assembly is approaching the retracted condition from the one extended condition and a second surface for effecting operation of said shock absorber assembly when said shuttle assembly is approaching the retracted condition from the other extended condition. K

8. A shuttle assembly as set forth in claim 7 wherein said first, second and third means are all positioned along a plane extending parallel to the path of movement of said load supporting section when said shuttle assembly is operated between the retracted condition and the extended condition.

9. A shuttle assembly as set forth in claim 6 further including an intermediate section mounted between said base section and said load supporting section, said drive means being operable to move said intermediate section at a first speed relative to said base section upon operation of said shuttle assembly between the retracted and extended conditions and to simultaneously therewith move said load supporting section relative to said intermediate section at a second speed which is greater than said first speed.

10. A shuttle assembly operable between a retracted condition and an extended condition to move a load, said shuttle assembly comprising a base section, an intermediate section operatively connected with and mounted for movement relative to said base section, a load-supporting section operatively connected with and mounted for movement relative to said intermediate section, and drive means for moving said intermediate section relative to said base section upon operation of said shuttle assembly between the retracted and extended conditions and for moving said load supporting section relative to said intennediate section upon operation of said shuttle assembly between the retracted and extended conditions, said drive means including a first rack means mounted on said intermediate section, a first pinion means operatively connected with said base means and mounted in meshing engagement with said first rack means whereby rotation of said first pinion means moves said first rack means and said intermediate section relative to said base section, first sprocket means rotatably mounted at one end portion of said intermediate section, second sprocket means rotatably mounted at another end portion of said intermediate section, a chain loop extending between, and meshingly engaging said first and second sprocket means, said chain loop being operatively connected to said base section so that the movement of said intermediate section relative to saidbase section under the influence of said first rack means and said first pinion means causes said chain loop to move relative to said base section to rotate said first and second sprocket means relative to said intermediate section, second rack means mounted on said load supporting section, second pinion means mounted on said one end portion of said intermediate section for driving engagement with said second rack means, said second pinion means being operatively connected with said first sprocket means whereby rotation of said first sprocket means under the influence of said chain a V a loop rotates said second pinion means, and third pinion means mounted on said other end portion of said intermediate section for driving engagement with said second rack means, said third pinion means being operatively connected with said second sprocket means whereby rotation of said second sprocket means under the influence of said chain loop rotates said third pinion means, said first pinion means being rotatable in one direction to drive said first rack means and said intermediate section in a first direction and to thereby move said chain loop relative to said base section to rotate said first and second sprocket means, said second pinion means being 

1. A shuttle assembly operable between a retracted condition and an extended condition to move a load, said shuttle assembly comprising a base section, an intermediate section operatively connected with the mounted for movement relative to said base section, a load supporting section operatively connected with and mounted for movement relative to said intermediate section, and drive means for moving said intermediate section through a first distance relative to said base section upon operatIon of said shuttle assembly between the retracted and extended conditions and for moving said load supporting section through a second distance relative to said intermediate section upon operation of such shuttle assembly between the retracted and extended conditions, said second distance being larger than said first distance so that said load supporting section projects further from said intermediate section than said intermediate section projects from said base section when said shuttle assembly is in the extended condition; the improvement comprising drive means including a first drive chain having a portion fixedly secured to said base section, first sprocket means which is operatively connected to said intermediate section and cooperates with said first drive chain, a second drive chain having a portion fixedly secured to said load supporting section, and second sprocket means which cooperates with said second drive chain and is rotated in response to rotation of said first sprocket means to thereby effect the aforesaid movement of said load supporting section, said first sprocket means being rotated in response to the aforesaid movement of said intermediate section relative to said base section.
 2. A shuttle assembly as set forth in claim 1 wherein said second sprocket means has a larger effective diameter than said first sprocket means to enable said drive means to move said load supporting section relative to said intermediate section at greater speed than the speed at which said intermediate section is moved relative to said base section upon operation of said shuttle assembly between the retracted and extended conditions.
 3. A shuttle assembly as set forth in claim 1 further including shock absorber means for retarding movement of said load supporting and intermediate sections when said shuttle assembly approaches either one of said extended and retracted conditions.
 4. A shuttle assembly as set forth in claim 1 wherein said drive means is operable to extend and shuttle assembly in either of two opposite direction from said retracted condition to either of two extended conditions, said shuttle assembly further including a shock absorber assembly operatively connected with said base and load-supporting sections, first stop means for operating said shock absorber assembly when said shuttle assembly approaches one of said extended conditions, second stop means for operating said shock absorber assembly when said shuttle assembly approaches the other extended condition, and third means for operating said shock absorber assembly when said shuttle assembly approaches said retracted condition from either of said operated conditions.
 5. A shuttle assembly as set forth in claim 4 wherein said first, second and third means are all mounted for movement with said intermediate section and are all aligned along a plane extending parallel to the path of movement of said shuttle assembly between said retracted and extended conditions.
 6. A shuttle assembly operable between a retracted condition and either of two extended conditions to move a load, said shuttle assembly comprising a base section, a load supporting section movable relative to said base section, drive means for moving said load-supporting section in one direction to operate said shuttle assembly from the retracted condition to one of the extended conditions and for moving said load supporting section in a direction opposite to said one direction to operate said shuttle assembly to the other extended condition, operatively connected with said base section, first stop means operatively connected with said load supporting section for operating said shock absorber assembly when said shuttle assembly is approaching the one extended condition, second stop means spaced from said first stop means and operatively connected with said load supporting section for operating said shock absorber assembly when said shuttle assembly is approaching the other extended condition, and third means located between saId first and second stop means and operatively connected with said load-supporting section for operating said shock absorber assembly when said shuttle assembly is approaching the retracted condition from either of the extended conditions.
 7. A shuttle assembly as set forth in claim 6 wherein said third means includes a first surface for effecting operation of said shock absorber assembly when said shuttle assembly is approaching the retracted condition from the one extended condition and a second surface for effecting operation of said shock absorber assembly when said shuttle assembly is approaching the retracted condition from the other extended condition.
 8. A shuttle assembly as set forth in claim 7 wherein said first, second and third means are all positioned along a plane extending parallel to the path of movement of said load supporting section when said shuttle assembly is operated between the retracted condition and the extended condition.
 9. A shuttle assembly as set forth in claim 6 further including an intermediate section mounted between said base section and said load supporting section, said drive means being operable to move said intermediate section at a first speed relative to said base section upon operation of said shuttle assembly between the retracted and extended conditions and to simultaneously therewith move said load supporting section relative to said intermediate section at a second speed which is greater than said first speed.
 10. A shuttle assembly operable between a retracted condition and an extended condition to move a load, said shuttle assembly comprising a base section, an intermediate section operatively connected with and mounted for movement relative to said base section, a load-supporting section operatively connected with and mounted for movement relative to said intermediate section, and drive means for moving said intermediate section relative to said base section upon operation of said shuttle assembly between the retracted and extended conditions and for moving said load supporting section relative to said intermediate section upon operation of said shuttle assembly between the retracted and extended conditions, said drive means including a first rack means mounted on said intermediate section, a first pinion means operatively connected with said base means and mounted in meshing engagement with said first rack means whereby rotation of said first pinion means moves said first rack means and said intermediate section relative to said base section, first sprocket means rotatably mounted at one end portion of said intermediate section, second sprocket means rotatably mounted at another end portion of said intermediate section, a chain loop extending between and meshingly engaging said first and second sprocket means, said chain loop being operatively connected to said base section so that the movement of said intermediate section relative to said base section under the influence of said first rack means and said first pinion means causes said chain loop to move relative to said base section to rotate said first and second sprocket means relative to said intermediate section, second rack means mounted on said load supporting section, second pinion means mounted on said one end portion of said intermediate section for driving engagement with said second rack means, said second pinion means being operatively connected with said first sprocket means whereby rotation of said first sprocket means under the influence of said chain loop rotates said second pinion means, and third pinion means mounted on said other end portion of said intermediate section for driving engagement with said second rack means, said third pinion means being operatively connected with said second sprocket means whereby rotation of said second sprocket means under the influence of said chain loop rotates said third pinion means, said first pinion means being rotatable in one direction to drive said first rack means and said intermediate section in a fiRst direction and to thereby move said chain loop relative to said base section to rotate said first and second sprocket means, said second pinion means being driven by rotation of said first sprocket means to drive said second rack means and load supporting section in said first direction, said first pinion means being rotatable in another direction opposite from said one direction to drive said first rack means and said intermediate section in a second direction and to thereby move said chain loop relative to said base section to rotate said first and second sprocket means, said third pinion means being driven by rotation of said second sprocket means to drive said second rack means and said load-supporting section in said second direction. 